1. Field of the Invention
The present invention relates to a book-binding apparatus for automatically gluing a sheet bundle to book-bind it.
2. Related Background Art
There have been proposed on-line systems in which a series of operations from an image forming operation to a book-binding operation for book-binding a sheet bundle discharged from an image forming apparatus and comprised of sheets on which images were formed are performed continuously. In such on-line systems, a plurality of imaged sheets (sheet bundle) are book-bound by gluing the sheet bundle. In this gluing and book-binding operation, a strip-shaped bind tape on which hot melt adhesive is coated is used.
When a plurality of imaged sheets being moved through the on-line system are book-bound, first of all, the plurality of imaged sheets being moved are stacked on an alignment tray to align the sheets with each other as a sheet bundle. Then, the aligned sheet bundle is sent to a book-binding portion, where a bound edge of the sheet bundle is urged against a bind tape which was pre-heated by a tape heating means (heaters). As a result, adhesive coated on the bind tape flows into between the sheets, thereby gluing the sheet bundle.
Normally, the bind tape is wound around a tape reel, and, whenever a sheet bundle is book-bound, the bind tape is supplied from the tape reel and is then cut to a predetermined length by a cutter. The cut tape is sent to the book-binding portion. The strip-shaped bind tape cut to the predetermined length is set at the book-binding portion and is previously heated by the tape heating means before the aligned sheet bundle is conveyed to the book-binding portion. The pre-heating time for the bind tape is determined by the material of the adhesive, and the strip-shaped bind tape is conveyed to the book-binding portion in consideration of the pre-heating time. Meanwhile, the tape heating means is maintained in an ON condition to reach a temperature optimum to pre-heat the bind tape. (The reason for pre-heating the bind tape is that the adhesive is melted to an appropriate condition to perform high quality gluing.)
In case of the conventional on-line systems (book-binding apparatuses), a timing for conveying the strip-shaped bind tape to the book-binding portion (bind tape conveying timing) is determined to start at a time point when a predetermined time period is elapsed from the initiation of the book-binding operation. However, as is in the present days, when sheets having various different attributes are to be book-bound, in the above-mentioned conventional on-line systems, the productivity of the entire system may be decreased or the high quality gluing cannot often be performed.
That is to say, as is in the above-mentioned conventional on-line systems, when the strip-shaped bind tape is conveyed to the book-binding portion at the predetermined conveying timing, regarding a sheet bundle which can be aligned earlier, the conveying timing for conveying the sheet bundle to the book-binding portion must be delayed so that the sheet bundle is prevented from being conveyed to the book-binding portion before the pre-heating of the bind tape is finished. Consequently, the total book-binding time is lengthened, thereby decreasing the productivity of the entire system. On the other hand, regarding a sheet bundle which can be aligned later, since the sheet bundle cannot reach the book-binding portion immediately after the pre-heating of the bind tape is finished, the adhesive is melt excessively, thereby making the high quality gluing impossible.
Incidentally, in this specification, factors for determining the alignment time of the sheet bundle (for example, a size of the sheet, a conveying direction of the sheet, and post-treatment of the sheet) are referred to as "attributes" of the sheet.